1. Field of the Invention
The present invention relates to multi-line wireless telephone systems.
2. Description of the Related Art
The use of telephones and telephone systems, including wireless telephone systems, is widespread. In wireless telephone systems, a cordless or wireless telephone handset unit communicates via either analog or digital radio signals with a base unit, which is typically, connected via a standard telephone line to an external telephone network. In this manner, a user may employ the wireless handset to engage in a telephone call with another user through the base unit and the telephone network.
Multi-line wireless telephone systems are also in use in various situations, such as businesses with many telephone users. Such systems employ a handset that communicates with up to N handsets simultaneously, typically with digital communications schemes, such as time division multiple access (TDMA). It is desirable to implement the features of current private branch exchange (PBX) systems in a multi-line wireless telephone system. Conventional multi-line wireless telephone systems typically must work within a specified bandwidth and modulation format, which thus constrains the maximum capacity of the radio-frequency (RF) channel used to transmit signals between the base unit and the operating or active handsets.
One problem that arises due to the fixed capacity or bandwidth available for such telephone systems and the inflexibility of such systems is that the available channel capacity may be inefficiently utilized when not all handsets are operating. This is because, in some such systems, such as that disclosed for example, in European Patent Application No. 0 587 225 A2, the channel capacity is selected so that all N handsets can operate simultaneously, if necessary. However, when less than N handsets are operating, channel capacity is underutilized. Overall signal quality may be reduced in order to also reduce the total bandwidth (and thus the amount wasted when not all handsets are employed), but this reduces quality needlessly in some cases, for example where only one handset is operating and there is enough total channel capacity available to allow the single handset to communicate at high quality.